Assertion (A): Biconvex lens can form virtual image of a virtual object.
Reason (R): Nature of lens depends on refractive index of surrounding.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
A biconvex lens can form a virtual image of a virtual object. The nature of a lens (converging/diverging) depends on the refractive index of the lens material relative to the surrounding medium. Therefore, both A and R are true, and R is the correct explanation of A.
Assertion (A): In clear weather, sky appears to be blue not violet.
Reason (R): In clear atmosphere, light of shorter wavelength is scattered more as compared to light of longer wavelength.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is true; violet light scatters most, but our eyes are more sensitive to blue. Reason (R) is true; Rayleigh scattering is inversely proportional to the fourth power of wavelength, scattering shorter wavelengths more effectively. Reason (R) correctly explains Assertion (A).
Assertion (A): During sunset and sunrise sun appears to be red.
Reason (R): During sunrise or sunset, sun emits electromagnetic radiations of comparatively higher wavelength only.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is true; at sunrise/sunset, sunlight travels longer through the atmosphere, scattering away shorter wavelengths (blue) and leaving longer wavelengths (red). Reason (R) is false; the sun emits all wavelengths. The perceived color is due to atmospheric scattering, not selective emission.
Assertion (A): A virtual image can’t be caught on screen, yet we see a virtual image. We are obviously bringing it on to the screen, i.e. the retina.
Reason (R): The retina is a special type of screen present in the back of eye consisting of nerve fibre which can catch both real & virtual image.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is true; virtual images cannot be projected onto a physical screen. Reason (R) is false; the retina, acting as a screen, can only detect real images formed by the eye's lens. Our brain interprets virtual images.
Assertion (A): In a magnifying glass, the angle subtended by an object at the eye is equal to the angle subtended by its virtual image at the eye. Still the magnifying glass provides angular magnification.
Reason (R): Magnifying glass produce a virtual magnified image of the object.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is false. Angular magnification occurs precisely because the virtual image subtends a larger angle at the eye than the object alone. Reason (R) is true; a magnifying glass (convex lens) forms a virtual, upright, and magnified image.
Assertion (A): Although the surface of goggles lens are curved, it does not have any power.
Reason (R): In case of goggles, both the curved surfaces have equal radius of curvature and have centre of curvature on the same side
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Protective goggle lenses do not alter vision, implying their optical power is zero. Thus, (A) is true.
The power of a lens is given by \(P = (n-1)(\frac{1}{R_1} - \frac{1}{R_2})\). If the surfaces have equal radii of curvature and their centers are on the same side (as in a meniscus lens where both surfaces curve in the same direction), then \(\frac{1}{R_1} - \frac{1}{R_2} = 0\), resulting in (P = 0). This explains why curved goggle lenses can have no power. Thus, (R) is true and is the correct explanation of (A).
Assertion (A): For better resolution, in microscope we prefer “Oil immersed object”.
Reason (R): Refractive index of oil is closer to the refractive index of objective glass.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Oil immersion is used in microscopes to increase the numerical aperture (NA) and thus improve resolution. Thus, (A) is true.
The refractive index of the immersion oil is chosen to be very close to that of the objective lens glass, which minimizes refraction and maximizes the angle of light collected, increasing NA. Thus, (R) is true and is the correct explanation of (A).
Assertion (A): Rainbow is an example of the dispersion of sunlight by the water droplets.
Reason (R): Light of shorter wavelength is scattered much more than light of larger wavelength.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Rainbows are formed due to dispersion and total internal reflection of sunlight by water droplets. Thus, (A) is true.
Rayleigh scattering states that the intensity of scattered light is inversely proportional to the fourth power of its wavelength \((I \propto 1/\lambda^4)), meaning shorter wavelengths (blue, violet) are scattered more than longer wavelengths (red). Thus, (R) is true.
However, (R) explains scattering, which is distinct from dispersion (dependence of refractive index on wavelength) responsible for the separation of colors in a rainbow. So, (R) does not explain (A).
Assertion (A): The persistence of vision \(1/16\) second is used in cinematography.
Reason (R): The human eye forms the real image of an object at its retina.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true; the brain's retention of images for about \(1/16\) second creates motion from rapid stills. Reason (R) is true; the eye's lens system forms a real, inverted image on the retina. R describes a fundamental eye function, which is a prerequisite for A but not its direct explanation. Thus, both are true, but R does not explain A.
Assertion (A): A single lens cannot be free from chromatic aberration.
Reason (R): When light passes through single lens dispersion must occur.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Chromatic aberration occurs because the refractive index of a lens material varies with wavelength (dispersion). A single lens always causes dispersion, leading to different focal points for different colors. Thus, both (A) and (R) are true, and (R) explains (A).